Some people set their own problems aside in order to help others because they don't feel as though their own problems matter enough to take precedent. It feels selfish to say no when it really shouldn't.

You're allowed to have your own problems, just like you're allowed to be hungry even though other people in the world might be literally starving. You can be aware of someone's suffering and it doesn't make you any less "hungry", so to speak.

It might be a stupid analogy, but it works for me.

It's necessary to know when your own problems deserve more attention, even if it happens at the cost of not being able to help someone else.

This is important because there are times where we set our own shit aside as a means of avoiding our own problems. By helping someone else instead of taking time to address your own concerns, you still get to feel as though you've at least accomplished something.

When that happens regularly, not only does it cause problems to fester, but it has a funny way of creating a sense of resentment towards the people we helped during the times when we should have been helping ourselves.

That becomes especially true if they don't reciprocate the same level of support that you offered, and you have to dig deep to accept that you helped them because you wanted to help; it wasn't done as a favor that they should owe you for. Otherwise, you just end up being cynical about it all.

tl;dr You don't have to feel bad about feeling bad. It takes some time to enforce boundaries with people and then be able to act on the belief that they know you're not ignoring them or otherwise being inconsiderate. They won't hate you for it, and if they do, that's something to take a hard look at and wonder why they don't have a mutual respect for your priorities.